Conventional microwave ovens have a defrosting facility which works either by delivering microwave power to the oven cavity for a time duration set by the user or for a fixed time duration, in the latter case the user performing repeated defrosting operations for larger food items. The invention aims to provide a microwave oven, and a method of defrosting, in which the user merely needs to choose the defrosting function, after which follows a defrosting program dependent on the size of food item being defrosted.